I am having some problems with network performance speed on a Linux server running Ubuntu 9.10. Transfer speeds on all types of traffic are around 1.5MB/s on a 1000mbit/s wired ethernet connection. This server has achieved 55MB/s over samba in the recent past. I have not changed the hardware or network set-up. I do run updates on a regular basis and the latest and greatest from Ubuntu's repositories is running on this machine.

Hardware set-up

Desktop Windows PC - 1000 switch - 1000 switch - Linux server

All switches are netgear, and they all show a green light for their connections which means the connection is 1000mbit/s. The lights are yellow when the connection is only 100mbit/s. Other diagnostic information:

The server thinks its got a 1000mbit/s connection. I have tested the speed of transfer by copying files using Samba. I have also used netcat (nc target 10000 < aBigFile) on the server to transfer to Windows (nc -l -p 10000) and saw similar levels of poor performance.

5 Answers
5

In my professional experience, I've struggled to get good solid network performance with Samba on GNU/Linux. You mentioned you have achieved speeds of 55 MBps with it, which I believe, so I'm guessing something else is definitely at play.

However, have you tried NFS, FTP and SCP? Are the bandwidth issues consistent across the different protocols? If so, it's likely narrowed down to the physical connection. If you get inconsistent results, then it's likely a software problem.

Aside from testing the other protocols, are you using encryption on the transfer? For example, using rsync -z is sweet for enabling compression, but it's comes at a CPU cost, which severely impacts overall speed of the transfer. If using SSH with rsync, then you have encryption on top of compression, and your CPU will be under a bit of stress, causing severe speed penalties.

If at all possible, to remove most doubt that it is indeed an OS/driver/card issue, connect the computers together using a cross over cable. This will remove the switch and other possible networking issues from your equation.